Computer interconnection and communications systems are generally referred to as networks. Networks are typically classified according to their geographical extent as local area networks (LANs), metropolitan area networks (MANs) and wide area networks (WANs). The Internet is a global network of computer networks. Computers attached to the Internet can communicate by sending messages to each other via the Internet.
Telephone networks such as the public switched telephone network (PSTN) have been dominating voice communications. Computer networking has grown side-by-side with telephone networks. The consolidation of voice and data communication on the Internet around an Internet protocol (IP) now allows sound enabled computers to exchange digitized audio messages via the Internet.
IP telephony uses the Internet for real-time audio communications where two or more participants can carry a conversation. The IP telephony is governed by the data network communications standard, known as the Internet protocol, that allows voice to ride on the data network.
Since IP telephony is capable of combining voice and data on a single line, IP telephony is advantages in instances where a single phone connection is used for on-line access. Additionally, through deployment of IP telephony international and long-distance telephone service providers can offer Internet phone calls to customers with software for multimedia PCs (personal computer).
Gateways are key components in every IP telephony infrastructure. FIG. 1 illustrates an exemplary IP telephony infrastructure. Gateways 130 offer the advantage of IP telephony by bridging between the traditional telephone network 120 and the Internet 110. For real-time communications through the Internet 110, gateways 130 provide audio conversion and perform call setup and termination.
Telephone-to-telephone 160 communications require two gateways 130. This configuration can be advantageously used for low-cost long distance and international calls. For example, a telephone call can be placed via the telephone network 120a in one country, and through a gateway 130a in this country the telephone call can be routed to a gateway 130b in a second country via the Internet 110. The second gateway 130b connects the call to the destination telephone 160b via the telephone network 120b in the second country. The routing through the Internet allows bypassing of the international connection fees.
In addition to gateways 130, an important component in IP telephony infrastructure is a gatekeeper 140. A gatekeeper acts as a central point for all calls within its zone and provides call control services to registered terminals 150 and gateways 130 including balancing among multiple gateways 130. Routing of calls through gatekeepers 140 allows service providers to bill for calls placed through their network. Gatekeepers 140 also perform address translations to IP addresses and manage the communications bandwidth.
An umbrella protocol the governs IP telephony and provides the standard for audio, video, and data communications across IP-based networks, including the Internet, is known as the H.323 standard. Conformance with the H.323 standard intends to provide for transparent communications between gateways and terminals or single user devices (hereafter collectively referred to as “terminals”) without concern for compatibility. Implementation of the H.323 standard intends to allow for interoperability of applications from different vendors.
However, interoperability issues do come up. For example, some terminals may implement only a subset of the H.323 standard or interpret some fields differently. Terminals also lack capabilities that prevent their complete integration in and readiness for the IP telephony. Terminals do not perform functions such as authentication, billing and call cutoff, and cannot find an appropriate gateway to connect to. Normally, terminals are connected to the Internet intermittently, only when logged on. Hence, terminals are not always ready to accept incoming calls. Finally, when calling a destination terminal, telephone users do not know the IP address of destination terminal. The present invention addresses the aforementioned interoperability issues and related problems.